Structure and magnetic properties of lanthanum and calcium-deficient La0.5Ca0.5MnO3 manganites

The effects of small amounts (5%) of calcium and lanthanum-deficiency on the structure and magnetic properties of polycrystalline La0.5Ca0.5MnO3 manganite have been investigated. Our samples have been synthesized using the conventional solid-state reaction technique at high temperatures. Rietveld analysis confirms the orthorhombic perovskite structure with Pnma space group. The calcium-deficiency leads to an increase of the unit cell volume while the lanthanum-deficient material exhibits a decrease in the unit cell volume compared to the parent compound. At high temperature, La0.5Ca0.5MnO3 is a paramagnetic insulator and upon cooling it exhibits a paramagnetic-ferromagnetic transition at Tc approximate to 230 K followed by a ferromagnetic-antiferromagnetic one at T-N approximate to 150 K. Five percent of Ca-deficient destroys the ferromagnetic-antiferromagnetic transition observed at low temperature in the parent compound while the sample with 5% of La-deficient behaves as antiferromagnet below 100 K. (c) 2006 Elsevier B.V. All rights reserved.